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Structural Behaviour of Traditional Timber Frames and It’s Reinforcement


Wen-Shao Chang (京都大学生存圏研究所・JSPS特別研究員)


  • ミッション 4 (循環型資源・材料開発)


歴史的な建造物、その多くは木構造であるが、耐震性能は地震多発地域に位置する国々にとって大きな関心事である。1999 年に台湾で発生した Chi-Chi 地震では多くの伝統的な木構造が甚大な被害を被ったが、崩壊には至らなかった。


まず第一に、何も補強していない異なる 3 種類の試験体を作成して、接合部と耐力壁の仕様の違いが全体の構造性能に及ぼす影響を考察した。その結果、耐力壁の割合いが大きい架構ほど高い耐震性能を示すだけではなく、架構中に含まれる様々な接合部によっても影響されることが分かった。実験で破壊した試験体の一つを補修して再試験をしたが、補修だけでは十分な耐力は確保できず、当初の 40 % 程度の耐力しか得られなかった。一方、残り 2 体については、上述した方法で補強して再試験をした結果、ほぼ当初の強度を再現することができた。理論と実験を比較したところ、採用した解析手法はこの種の問題に対応するのに妥当な方法であることが分かった。これらの発表は、地震後に解体せざるを得なくなった伝統的木構造の補強方法についても何か新しい手法の提案が必要であることを示唆している。

Seismic capacities of historic buildings, among which timber structures are dominant, are of interest for those countries located in seismic-prone area. In Chi-Chi earthquake of 1999, many traditional timber structures in Taiwan were severely damaged but not collapsed. This resulted in urgent need to develop a new method to reinforce or repair these traditional timber structures without dismantling the whole timber frame. To increase the seismic capacity of traditional timber frames, we proposed to use hard wood strip to reinforce the wooden shear wall and use hard wood dowel to reinforce the timber connections. This presentation depicts the experimental results and compares these results with results obtained from analytical approach.

In the first stage, three various types of timber frames without any reinforcement were fabricated to discuss the effect of connections types and variation of shear walls on entire strucutral behaviour. The results not only demonstrates that timber frame with high shear wall ratio will have higher earthquake-resistance capacity, but also indicates that structural behaviour will be affected by different connection types within the frames.

One of the failed structural frames was repaired and two of them were reinforced after test. The results revealed that the repaired specimens cannot have sufficient earthquake resistance capacity and is about 40 % reduction in strength compared with original strength, whilst the strength of the specimens show nearly fully recover after repairment. The comparison of experimental and analytical results showed that the analytical approach adopted is appropriate to analyze this kind of structures. This presentation further implies we should develop a new reinforcement method for those traditional timber structures which require dismantling after the earthquake.